Bottom Line:
For comparing discriminatory ability and responsiveness to change, multivariable regression models were used to estimate the effect sizes of various health indicators on the index scores.Whenever appropriate, the 90% confidence intervals (90% CI) were compared to predefined equivalence margins.This study provided the first evidence supporting the validity of the mapping function for converting EQ-5D-5L profile data into a utility-based index score.

Affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore.

ABSTRACT

Objective: Utility values of health states defined by health-related quality of life instruments can be derived from either direct valuation ('valuation-derived') or mapping ('mapping-derived'). This study aimed to compare the utility-based EQ-5D-5L index scores derived from the two approaches as a means to validating the mapping function developed by van Hout et al for the EQ-5D-5L instrument.

Methods: This was an observational study of 269 breast cancer patients whose EQ-5D-5L index scores were derived from both methods. For comparing discriminatory ability and responsiveness to change, multivariable regression models were used to estimate the effect sizes of various health indicators on the index scores. Agreement and test-retest reliability were examined using intraclass correlation coefficient (ICC). Whenever appropriate, the 90% confidence intervals (90% CI) were compared to predefined equivalence margins.

Results: The mean difference in and ICC between the valuation- and mapping-derived EQ-5D-5L index scores were 0.015 (90% CI = 0.006 to 0.024) and 0.915, respectively. Discriminatory ability and responsiveness of the two indices were equivalent in 13 of 15 regression analyses. However, the mapping-derived index score was lower than the valuation-derived index score in patients experiencing extreme health problems, and the test-retest reliability of the former was lower than the latter, for example, their ICCs differed by 0.121 (90% CI = 0.051 to 0.198) in patients who reported no change in performance status in the follow-up survey.

Conclusion: This study provided the first evidence supporting the validity of the mapping function for converting EQ-5D-5L profile data into a utility-based index score.

Mentions:
A total of 280 patients completed the baseline survey. Two patients with missing values and nine proxy-administered patients were excluded, leaving 269 patients. Table 1 summarizes their demographic and clinical characteristics. The mean (standard deviation) score of the valuation- and mapping-derived EQ-5D-5L indices for the sample was 0.811 (0.186) and 0.796 (0.250), respectively, at baseline (Table 2). The difference of 0.015 (90 % CI = 0.006 to 0.024) was small in magnitude and the 90 % CI totally fell within the equivalence margin of ±0.05, indicating equivalence of the two indices. Both indices attained the maximum value of 1, while the lowest score was −0.111 and −0.370 for the valuation- and mapping-derived index, respectively. The ICC between the two indices was 0.915. Their Bland-Altman plot shows that, for the 12 patients (4.5 %) with the lowest health utility value in the sample, the mapping-derived index score (mean = −0.118, range = −0.370 to 0.118) was apparently smaller than the valuation-derived index score (mean = 0.261, range = −0.111 to 0.487) (Fig. 1). All the 12 patients experienced extreme problems in at least one EQ-5D-5L dimension.Table 1

Mentions:
A total of 280 patients completed the baseline survey. Two patients with missing values and nine proxy-administered patients were excluded, leaving 269 patients. Table 1 summarizes their demographic and clinical characteristics. The mean (standard deviation) score of the valuation- and mapping-derived EQ-5D-5L indices for the sample was 0.811 (0.186) and 0.796 (0.250), respectively, at baseline (Table 2). The difference of 0.015 (90 % CI = 0.006 to 0.024) was small in magnitude and the 90 % CI totally fell within the equivalence margin of ±0.05, indicating equivalence of the two indices. Both indices attained the maximum value of 1, while the lowest score was −0.111 and −0.370 for the valuation- and mapping-derived index, respectively. The ICC between the two indices was 0.915. Their Bland-Altman plot shows that, for the 12 patients (4.5 %) with the lowest health utility value in the sample, the mapping-derived index score (mean = −0.118, range = −0.370 to 0.118) was apparently smaller than the valuation-derived index score (mean = 0.261, range = −0.111 to 0.487) (Fig. 1). All the 12 patients experienced extreme problems in at least one EQ-5D-5L dimension.Table 1

Bottom Line:
For comparing discriminatory ability and responsiveness to change, multivariable regression models were used to estimate the effect sizes of various health indicators on the index scores.Whenever appropriate, the 90% confidence intervals (90% CI) were compared to predefined equivalence margins.This study provided the first evidence supporting the validity of the mapping function for converting EQ-5D-5L profile data into a utility-based index score.

Affiliation:
Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore.

ABSTRACT

Objective: Utility values of health states defined by health-related quality of life instruments can be derived from either direct valuation ('valuation-derived') or mapping ('mapping-derived'). This study aimed to compare the utility-based EQ-5D-5L index scores derived from the two approaches as a means to validating the mapping function developed by van Hout et al for the EQ-5D-5L instrument.

Methods: This was an observational study of 269 breast cancer patients whose EQ-5D-5L index scores were derived from both methods. For comparing discriminatory ability and responsiveness to change, multivariable regression models were used to estimate the effect sizes of various health indicators on the index scores. Agreement and test-retest reliability were examined using intraclass correlation coefficient (ICC). Whenever appropriate, the 90% confidence intervals (90% CI) were compared to predefined equivalence margins.

Results: The mean difference in and ICC between the valuation- and mapping-derived EQ-5D-5L index scores were 0.015 (90% CI = 0.006 to 0.024) and 0.915, respectively. Discriminatory ability and responsiveness of the two indices were equivalent in 13 of 15 regression analyses. However, the mapping-derived index score was lower than the valuation-derived index score in patients experiencing extreme health problems, and the test-retest reliability of the former was lower than the latter, for example, their ICCs differed by 0.121 (90% CI = 0.051 to 0.198) in patients who reported no change in performance status in the follow-up survey.

Conclusion: This study provided the first evidence supporting the validity of the mapping function for converting EQ-5D-5L profile data into a utility-based index score.